Onset or exacerbation of multiple organ failure can be classified into the following three categories with respect to mechanism: (1) parallel induction of several organ disorders due to the same factor, (2) induction of a specific organ dysfunction due to disorder of an organ; and (3) participation of an iatrogenic factor. Excessive insults due to severe trauma, major surgeries, infectious diseases, or shock, either directly or through various kinds of mediator, participate in the onset or deterioration of multiple organ failure by mechanism (1). In the case of multiple organ failure accompanied with organ disorder due to trauma or primary hepatic insufficiency, participation of mechanism (2) through organ correlation mechanism will largely contribute to the onset or deterioration thereof. By mechanism (3), medical care carried out during intensive care or care to correspond with an organ disorder may result in the other organ disorder. In patients, these three mechanisms participate to the development or deterioration of multiple organ failure in a complex manner. The prognosis of patients of multiple organ failure is generally very poor and, in fact, the survival rate is low as 20–30% in spite of a wide variety of corresponding treatments.